In one form of rivet setting tool for setting screwthreaded rivet nuts or blind rivet nuts or the like, referred to hereinafter for the sake of simplicity as rivet nuts, the tool comprises a forward feed assembly which is actuable to perform the rivet nut upsetting operation and which is adapted to impart an axial movement to the screwthreaded pin or the tensile pin for setting of the rivet. The tool comprises a trigger which, by applying a pressure to a control valve rod, moves the rod to close or open communicating openings for a pressure fluid in the tool, to provide for actuation thereof. The forward feed assembly comprises a piston cylinder arrangement including a pressing piston and a working piston and the tool itself comprises a body portion in which the working piston is disposed, together with a working piston rod, and a handle portion in which the pressing piston with its pressing chambers is arranged.
The above-mentioned trigger of the tool is arranged to control the flow of pressure fluid in the handle portion of the tool and is disposed at a location on the tool where the handle portion connects to the body portion carrying the working piston of the tool. The control valve rod which is actuated by the trigger extends longitudinally in the handle portion and the upper end of the rod is pivotally connected to the trigger by way of an intermediate connecting lever. The trigger itself is mounted pivotably about a pivot pin and displaces the control valve rod by way of the intermediate lever, when the trigger is caused to pivot about its pivot pin by for example a finger pressure applied thereto.
That construction however suffers from the disadvantage that, when actuating the trigger to operate the tool, it is necessary to overcome certain pressure points in the movement of the trigger, which occur due to the fact that the pivotal movement of the trigger about its pivot mounting pin has to be converted into a translatory movement of the control valve rod by way of the intermediate lever. Furthermore, the design configuration is such that the actuating arrangement is comparatively susceptible to trouble and is complicated from the point of view of assembly.